Stress reduction feature for LOC lead frame

ABSTRACT

An LOC die assembly is disclosed including a die dielectrically adhered to the underside of a lead frame. The lead frame has stress relief slots formed in the undersides of the lead elements proximate the adhesive to accommodate filler particles lodged between the leads and the active surface of the die during transfer molding of a plastic encapsulant. The increased space created by the slots and flexure in the leads about the slots reduces point stresses on the active surface of the die by the filler particles. The increased flexure in the leads about the slots further enhances the locking of the leads in position with respect to the die.

This application is a continuation divisional continuation-in-part ofapplication Ser. No. 08/614,618, filed Mar. 13, 1996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention pertains to a “leads over chip” (LOC) semiconductor dieassembly, and more particularly to a method and apparatus for reducingthe stress resulting from lodging of filler particles present in plasticencapsulants between the undersides of the lead frame leads and theactive surface of the die and improved lead locking of the leads inposition over a portion of the active surface of a semiconductor dieassembly.

2. State of the Art

The use of LOC semiconductor die assemblies has become relatively commonin the industry in recent years. This style or configuration ofsemiconductor device replaces a “traditional” lead frame with a central,integral support (commonly called a die-attach tab, paddle, or island)to which the back surface of a semiconductor die is secured, with a leadframe arrangement wherein the dedicated die-attach support is eliminatedand at least some of the leads extend over the active surface of thedie. The die is then adhered to the lead extensions with an adhesivedielectric layer of some sort disposed between the undersides of thelead extensions and the die. Early examples of LOC assemblies areillustrated in U.S. Pat. No. 4,862,245 to Pashby et al. and U.S. Pat.No. 4,984,059 to Kubota et al. More recent examples of theimplementation of LOC technology are disclosed in U.S. Pat. Nos.5,184,208; 5,252,853; 5,286,679; 5,304,842; and 5,461,255. In instancesknown to the inventors, LOC assemblies employ large quantities orhorizontal cross-sectional areas of adhesive to enhance physical supportof the die for handling.

Traditional lead frame die assemblies using a die-attach tab place theinner ends of the lead frame leads in close lateral proximity to theperiphery of the active die surface where the bond pads are located,wire bonds then being formed between the lead ends and the bond pads.LOC die assemblies, by their extension of inner lead ends over the die,permit physical support of the die from the leads themselves, permitmore diverse (including centralized) placement of the bond pads on theactive surface, and permit the use of the leads for heat transfer fromthe die. However, use of LOC die assemblies in combination with plasticpackaging of the LOC die assembly has demonstrated some shortcomings ofLOC technology as presently practiced in the art.

One of the short comings of the prior art LOC semiconductor dieassemblies is that the tape used to bond to the lead fingers of the leadframe does not adequately lock the lead fingers in position for the wirebonding process. At times, the adhesive on the tape is not strong enoughto fix or lock the lead fingers in position for wire bonding as the leadfingers pull away from the tape before wire bonding. Alternately, thelead fingers will pull away from the tape after wire bonding of thesemiconductor die but before encapsulation of the semiconductor die andframe either causing shorts between adjacent wire bonds or the wirebonds to pull loose from either the bond pads of the die or lead fingersof the frame.

After wire bonding the semiconductor die to the lead fingers of the leadframe forming an assembly, the most common manner of forming a plasticpackage about a die assembly is molding, and, more specifically,transfer molding. In this process (and with specific reference to LOCdie assemblies), a semiconductor die is suspended by its active surfacefrom the underside of inner lead extensions of a lead frame (typicallyCu or Alloy 42) by a tape, screen print or spin-on dielectric adhesivelayer. The bond pads of the die and the inner lead ends of the frame arethen electrically connected by wire bonds (typically Au, although Al andother metal alloy wires have also been employed) by means known in theart. The resulting LOC die assembly, which may comprise the framework ofa dual-in-line package (DIP), zig-zag in-line package (ZIP), smalloutline j-lead package (SOJ), quad flat pack (QFP), plastic leaded chipcarrier (PLCC), surface mount device (SMD) or other plastic packageconfiguration known in the art, is placed in a mold cavity andencapsulated in a thermosetting polymer which, when heated, reactsirreversibly to form a highly cross-linked matrix no longer capable ofbeing re-melted.

The thermosetting polymer generally is comprised of three majorcomponents: an epoxy resin, a hardener (including accelerators), and afiller material. Other additives such as flame retardants, mold releaseagents and colorants are also employed in relatively small amounts.

While many variations of the three major components are known in theart, the focus of the present invention resides in the filler materialsemployed and its effects on the active die surface and improved leadlocking of the lead fingers of the frame.

Filler materials are usually a form of fused silica, although othermaterials such as calcium carbonates, calcium silicates, talc, mica andclays have been employed for less rigorous applications. Powdered fusedquartz is currently the primary filler used in encapsulants. Fillersprovide a number of advantages in comparison to unfilled encapsulants.For example, filers reinforce the polymer and thus provide additionalpackage strength, enhance thermal conductivity of the package, provideenhanced resistance to thermal shock, and greatly reduce the cost of thepolymer in comparison to its unfilled state. Fillers also beneficiallyreduce the coefficient of thermal expansion (CTE) of the compositematerial by about fifty percent in comparison to the unfilled polymer,resulting in a CTE much closer to that of the silicon or galliumarsenide die. Filler materials, however, also present some recognizeddisadvantages, including increasing the stiffness of the plasticpackage, as well as the moisture permeability of the package.

Another previously unrecognized disadvantage discovered by the inventorsherein is the damage to the active die surface resulting fromencapsulant filler particles becoming lodged or wedged between theunderside of the lead extensions and the active die surface duringtransfer molding of the plastic package about the die and the inner leadends of the LOC die assembly. The filler particles, which may literallybe jammed in position due to deleterious polymer flow patterns and flowimbalances in the mold cavity during encapsulation, place the active diesurface under residual stress at the points of contact of the particles.The particles may then damage the die surface or conductive elementsthereon or immediately thereunder when the package is further stressed(mechanically, thermally, electrically) during post-encapsulationhandling and testing.

While it is possible to employ a lower volume of filler in theencapsulating polymer to reduce potential for filler particle lodging orwedging, a drastic reduction in filler volume raises costs of thepolymer to unacceptable levels. Currently available filler technologyalso imposes certain limitations as to practical beneficial reductionsin particle size (currently in the 75 to 125 micron range, with thelarger end of the range being easier to achieve with consistency) and inthe shape of the filler particles. While it is desirable that particlesbe of generally spherical shape, it has thus far proven impossible toeliminate non-spherical flakes or chips which, in the wrong orientation,maximize stress on the die surface.

Ongoing advances in design and manufacturing technology provideincreasingly thinner conductive, semiconductive and dielectric layers instate-of-the-art die, and the width and pitch of conductors servingvarious purposes on the active surface of the die are likewise beingcontinually reduced. The resulting die structures, while robust andreliable for their intended uses, must nonetheless become morestress-susceptible due to the minimal strength provided by the minutewidths, depths and spacings of their constituent elements. The integrityof active surface die coats such as silicon dioxide, doped silicondioxides such as phosphorous silicate glass (PSG) or borophosphoroussilicate glass (BPSG), or silicon nitride, may thus be compromised bypoint stresses applied by filer particles, the result beingunanticipated shortening of device life if not immediate, detectabledamage or alteration of performance characteristics.

The aforementioned U.S. Pat. No. 4,984,059 to Kubota et al. doesincidentally disclose several exemplary LOC arrangements which appear togreatly space the leads over the chip or which do not appear to providesignificant areas for filler particle lodging. However, such structuresmay create fabrication and lead spacing and positioning difficulties.

In addition to solving the problems associated with filler particlelodging and damage, it is desirable to have improved lead locking of thelead fingers of the frame during operations involving the semiconductordie. If the lead fingers have increased flexibility, the adhesive usedto bond the lead frame to the semiconductor die is more effective inlocking the lead fingers in position. Previously, improving lead fingerlocking has been approached from the perspective of improved adhesives,rather than increasing the flexibility of the lead fingers.

From the foregoing, the prior art has neither provided for improvedlocking of the lead fingers to the semiconductor die, nor recognized thestress phenomenon attendant to transfer molding and the use of filledencapsulants, nor provided an LOC structure which beneficiallyaccommodates this phenomenon.

SUMMARY OF THE INVENTION

The present invention provides a lead-supported die assembly for an LOCarrangement that substantially reduces the stress that may otherwisepotentially form between the leads and the active die surface due to thepresence of filler particles of the polymer encapsulant and improvedlead locking of the leads in position over a portion of the activesurface of a semiconductor die assembly. Accordingly, each lead of thelead frame between the bonding location of the die and the edge of thedie is formed with a stress relief portion therein. The resultingenlarged volume of space between the leads and the active die surfacewill beneficially accommodate an increased amount of the underlyingfiller particle or particles of the polymer encapsulant. Accordingly, astacking of filler particles in which the filler particles try to forcethe lead away from the die thus causing stress in the connection betweenthe lead and the die is less likely to occur. Moreover, this stressrelief portion allows flexibility in bending and torsion in the leadsdue to stress created during the transfer molding process as well asother processes. The resulting lead flexure in response to the fillermaterial will produce an immediate reduction in the residual stressexperienced by the active die surface. This lessened residual stress iscarried forward in the encapsulated package after cure, permitting thepackage to better withstand the stresses of post-encapsulation handlingand testing, including the elevated potentials and temperaturesexperienced during burn-in, without adverse effects. The resulting leadflexure also allows improved lead finger locking to the tape as lessforce is transferred to the tape from the flexure of the lead fingerswhich force may cause the lead fingers to become dislodged therefromprior to the wire bonding operations or, subsequently, duringencapsulation of the assembly.

The LOC apparatus of the present invention comprises a lead frame towhich the active surface of a die is adhered by a LOC tape, permittingthe lead frame to physically support the die during pre-encapsulationhandling and processing such as wire bonding. The free ends of the leadshave a recessed portion formed therein extending over a longitudinallength of the lead end proximate the active surface of the die. Withsuch an arrangement, intrusion of filler particles between the innerlead ends and the active surface of the die during the encapsulationprocess is beneficially accommodated.

Stated in more specific terms and on the scale of an individual lead andthe underlying active surface of the die, proximate the dielectricadhesive (such as LOC tape, screen print or spin-on, as known in theart) disposed on the underside of a lead, the lead is minimized incross-sectional area along the lead axis. The design permits anincreased amount of filler particles to accumulate in this recessed areasuch that the filler is less likely to force the lead away from the die.Similarly, the lead may incorporate a arched or bowed portion proximateits bonding location to the die to accommodate an increased amount offiller particles between the lead an the active surface of the die. Thisdesign also permits the free end of the lead to flex in bending andtorsion about this arched or bowed portion, so as to bend or twist asrequired while being retained in position by the tape or in the presenceof a filler particle or particles lodged between that lead and the die.

It is contemplated, that this flexibility or stress reduction portion orfiller particle accommodation portion of the lead frame may be formed inseveral manners. For example, a certain amount of each lead finger whereflexibility, stress reduction or filler particle accommodation isdesired may have a portion of its thickness chemically etched away.Likewise, various erosion, electron beam, machining or other processesknown in the art may be utilized to reduce the thickness of the leadfinger at the desired location. The reduced thickness portion of thelead finger for flexibility, stress reduction and filler particleaccommodation may also be created by deformation, coining, stamping orother such methods known in the art to thin material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 comprises a flow chart of an exemplary process sequence forplastic package molding;

FIGS. 2A and 2B are side schematic views of a typical transfer molding,showing pre-molding and post-molding encapsulant positions;

FIG. 3 shows a top schematic view of one side of a transfer mold ofFIGS. 2A and 2B, depicting encapsulant flow and venting of the primarymold runner and the mold cavities wherein the die assemblies arecontained;

FIGS. 4A, 4B and 4C depict encapsulant flow scenarios for a mold cavity;

FIGS. 5A and 5B depict cross-sectional side views of prior art packagedSOJ semiconductor devices;

FIGS. 6A and 6B depict cross-sectional side views of a first embodimentof packaged SOJ semiconductor device according to the present invention;

FIGS. 7A and 7B depict cross-sectional side views of a second embodimentof packaged SOJ semiconductor device according to the present invention;

FIGS. 8A and 8B depict top views of a lead frame according to thepresent invention;

FIG. 9 depicts a partial cross-sectional side view of a third embodimentof packaged SOJ semiconductor device according to the present invention;and

FIG. 10 depicts a partial cross-sectional side view of a forthembodiment of packaged SOJ semiconductor device according to the presentinvention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

So that the reader may more fully understand the present invention inthe context of the prior art, it seems appropriate to provide a briefdescription of a transfer apparatus and method for forming a plasticpackage about an LOC die assembly. The term “transfer” molding isdescriptive of this process as the molding compound, once melted, istransferred under pressure to a plurality of remotely-located moldcavities containing die assemblies to be encapsulated.

FIG. 1 is a flow chart of a typical process sequence for plastic packagemolding. It should be noted that the solder dip/plate operation has beenshown as one step for brevity; normally plating would occur prior totrim and form.

FIGS. 2A and 2B show pre-molding and post-molding positions ofencapsulant during a transfer molding operation using a typical moldapparatus comprising upper and lower mold halves 10 and 12, each moldhalf including a platen 14 or 16 with its associated chase 18 or 20.Heating elements 22 are employed in the platens to maintain an elevatedand relatively uniform temperature in the runners and mold cavitiesduring the molding operation. FIG. 3 shows a top view of one side of thetransfer mold apparatus of FIGS. 2A and 2B. In the transfer moldapparatus shown, the encapsulant flows into each mold cavity 44 throughthe short end thereof.

In operation, a heated pellet of resin mold compound 30 is disposedbeneath ram or plunger 32 in pot 34. The plunger descends, melting thepellet and forcing the melted encapsulant down through sprue 36 and intoprimary runner 38, from which it travels to transversely-orientedsecondary runners 40 and across gates 42 into and through the moldcavities 44 through the short side thereof flowing across the dieassemblies 100, wherein die assemblies 100 comprising dies 102 withattached lead frames 104 are disposed (usually in strips so that a stripof six lead frames, for example, would be cut and placed in and acrossthe six cavities 44 shown in FIG. 3). Air in the runners 38 and 40 andmold cavities 44 is vented to the atmosphere through vents 46 and 48. Atthe end of the molding operation, the encapsulant is “packed” byapplication of a higher pressure to eliminate voids and reducenon-uniformities of the encapsulant in the mold cavities 44. Aftermolding, the encapsulated die assemblies are ejected from the cavities44 by ejector pins 50, after which they are post-cured at an elevatedtemperature to complete cross-linking of the resin, followed by otheroperations as known in the art and set forth in FIG. 1 by way ofexample. It will be appreciated that other transfer molding apparatusconfigurations, as well as variations in the details of the describedmethod are known in the art. However, none of such are pertinent to theinvention, and so will not be discussed herein.

Encapsulant flow in the mold cavities 44 is demonstrably non-uniform.The presence of the die assembly 100 comprising a die 102 with leadframe 104 disposed across the mid-section of a cavity 44 splits theviscous encapsulant flow front 106 into upper 108 and lower 110components. Further, the presence of the (relatively) large die 102 withits relatively lower temperature in the middle of a cavity 44 permitsthe flow front 106 on each side of the die 102 to advance ahead of thefront which passes over and under the die 102. FIGS. 4A and 4B show twomold cavity encapsulant flow scenarios where, respectively, the lowerflow front 110 and the upper flow front 108 lead the overall encapsulantflow front 106 in the cavity 44 containing the die assembly 100. FIG. 4Cdepicts the advance of a flow front 106 from above, before and after adie 102 is encountered, the flow being depicted as time-separatedinstantaneous flow fronts 106 a, 106 b, 106 c, 106 d, 106 e and 106 f.

Encapsulant filler particles, as noted above, become lodged between leadends and the underlying die surfaces. The non-uniform flowcharacteristics of the viscous encapsulant flow, as described above, maycause (in addition to other phenomena, such as wire sweep, which are notrelevant to the invention) particles to be more forcefully drivenbetween the leads and the die and wedged or jammed in place inlow-clearance areas. As the encapsulant flow front advances and the moldoperation is completed by packing the cavities, pressure insubstantially all portions of the cavities reaches hydrostatic. Withprior art lead and adhesive LOC arrangements, the relative inflexibilityof the tightly-constrained (adhered) lead ends maintains the pointstresses of the particles trapped under the leads. These residualstresses are carried forward in the fabrication process to post-cure andbeyond. When mechanical, thermal or electrical stresses attendant topost-encapsulation processing are added to the residual point stressesassociated with the lodged filler particles, cracking or perforation ofthe die coat may occur, with the adverse effects previously noted. Ithas been observed that filler particle-induced damage occurs morefrequently in close proximity to the adhesive, where lead flexurepotential is at its minimum.

To graphically illustrate the above description of particle lodging,FIG. 5A depicts a prior art packaged LOC assembly wherein a single lead112 extends over a die 102, with a segment of dielectric adhesive 114,in this instance a piece of Kapton™ polyamide tape, adhered to both thelead 112 and the active surface 116 of the die. As better illustrated inFIG. 5B (DETAIL A), filler particle 130, which is part of the packagingmaterial 123, is lodged between lead 112 and die surface 116. It isclear that the lead end 122 is tightly constrained from movement by theinflexibility of the attachment of the lead end 122 to the die 102 bythe adhesive 114. Moreover, the relative closeness of the lead 112 tothe active surface 116 and the inability of the lead 112 to flex orrelax to reduce stress occasioned by the presence of the filler particle130 may continue even after the encapsulant has reached hydrostaticbalance such that the filler particle 130 may become tightly lodgedbetween the lead 112 and the active surface 116.

FIG. 6A, and in better detail FIG. 6B, depicts, in contrast to the priorart, a packaged LOC arrangement according to the present invention,wherein a single lead end 122 also extends over die 102. Instead of thetight lead-to-die constraint provided by the prior art lead member, alead 112 having a slot or recess 113 formed therein by etching,machining, eroding, removing material with an electron beam, or otherprocesses known in the art is utilized to reduce the thickness of thelead 112 proximate the active surface 116 of the die 102 between theportion of the lead end 122 attached to the adhesive 114 and the outeredge 115 of the die 102. The recess 113 creates an enlarged space 117,compared to the prior art device, between the active surface 116 and thelead 112. Thus, a filler particle 130, of same size and shape as thatshown with respect to the prior art, while still positioned between thelead 112 and the active surface 116 cannot become lodged therebetween.Moreover, the stacking of such particles 130 to create a similar lodgingeffect is less likely to occur because of the increased space 117.

Additionally, because the recess 113 forms a thinned portion 119 along alongitudinal length of the lead 112, the free end 121 of the lead 112can flex in both bending and twisting or torsion away from the activesurface 116. Thus, a plurality of particles 130 that become stackedbetween the active surface 116 of the die 102 and the thinned portion119 do not cause the same amount of residual stress to the die surface116, due to the ability of the free end 121 to, in effect, relax andreach a steady state position under hydrostatic encapsulant pressure,which relaxation reduces the point stress of the particle contact withthe die surface to an acceptable level. Furthermore, the ability of thelead 112 being able to flex allows improved lead locking in position bythe adhesive 114.

FIGS. 7A and 7B depict an alternative arrangement according to thepresent invention, wherein the recess 113 formed in the free end 121 ofthe lead 112 between the lead 112 and the active surface 116 of the die102 is formed by bending, deforming, or otherwise arching the lead 112by coining, stamping or other such methods known in the art. As in theembodiment shown in FIGS. 6A and 6B, this recessed portion 113 createsadditional space between the lead 112 and the die surface 116 such thata particle 130 is less likely to become lodged therein. In addition, thefree end 121 of the lead 112 is allowed to deflect about the lead end122 at the flex point 111 to relieve stress created by stacking ofparticles 130 between the recess 113 and the surface 116 to reduce themagnitude of point-loading of the filler particle 130 against diesurface 116. As previously stated, the ability of the lead 112 to fleximproves the lead locking ability of the adhesive 114.

FIGS. 8A and 8B depict views of the lead frame and associated die inaccordance with the present invention. For purposes of clarity andperspective, the inner, solid line 220 in FIG. 8A is the periphery ofthe die onto which the lead frame is superimposed and to which the leadframe is adhesively secured. In FIGS. 8A and 8B, double-dashed line 200is the outer lateral border of the plastic package to be molded on eachlead frame. In FIG. 8A, dashed line 210 represents the portion of thelead ends 122 that are typically plated. The periphery of the adhesivesegments disposed between certain leads or buses and the die arerepresented by inner, solid lines 240. Further, the portion of each leadmember that has a stress relief portion formed therein, as describedbelow, is represented by dotted lines 250 in FIG. 8A and cross-hatchedfor purposes of clarity in FIG. 8B. For purposes of illustration, thesemiconductor die as illustrated comprises memory devices, such asdynamic random access memory (DRAM), or static random access memory(SRAM), although the invention has equal utility to any semiconductordevice wherein an LOC arrangement is employed.

FIG. 8A depicts an arrangement wherein a lead frame 150, superimposed ona die 102, is secured thereto with dielectric adhesive strips orelongated segments 152 running along each side of active die surface116. The inner lead ends 122 of the leads 112 thus extend inwardly overadhesive segments 152 toward a row of bond pads 124 running along thecenter of the die 100. The inner lead ends 122 are then wirebonded tothe bond pads by wires 151. As shown in FIGS. 9 and 10, filler particles130 that are stacked may become lodged under a lead end 112 may thuscause the free end 121 of the lead 112 to be forced away from the activesurface 116 of the die 102. However, the greater the space 117 the lesslikely it is that filler particles 130 will become stacked in such a wayas to cause stress in the lead to die attachment or impinge on theactive surface 116 of the die 102.

As illustrated in FIGS. 9 and 10, the recess 113 may be of various sizesand configurations and be located in a variety of positions along thelead 112. In FIG. 9, the recess portion 113 extends a relatively smalldistance into the lead element 112, forming a substantially rectangularslot. Moreover, the side wall 153 of the recess is substantiallycoincident with the edge 115 of the die 102. In comparison, the recess113 shown in FIG. 10 extends farther in depth into the lead element 112,forms a substantially trapezoidal slot and has an angled side wall 155extending a distance away from the edge 115 of the die 102.Additionally, the angled side wall 157 forming one side of the slot maybe adjacent the edge 159 of the tape 152 as shown in FIG. 10 or extendbeyond the edge 159 as shown in FIG. 9. In any case, the size and shapeof the recess 113 may vary according to the process used to form such arecess. For example, such that etching may form a recess 113 similar tothat shown in FIG. 10 and machining may form a recess similar to that inFIG. 9. The improved flexibility of the lead 112 due to recess 113enhances the lead locking ability of the adhesive strips or segments152.

Thus, it will be appreciated by those of ordinary skill in the art thatseveral different stress relief arrangements may be employed, asillustrated, with a single lead frame and die design, to createadditional space between the active surface of the die and the lead.Moreover, given the known mechanical characteristics of a lead frame ofa given material and thickness, as well as the lead configurations, theoptimum location and configuration of the stress relief portion may beeasily calculated, if required. Further, the minimum cross-sectionalarea of the lead frame at the location of the stress relief may becalculated. With that explanation, no further design details arebelieved to be necessary for practice of the invention by those ofordinary skill in the art. CAD (computer aided design) may easily, andpreferentially, be employed to make the foregoing determinations andarrive at one more optimum solutions for stress relief locations andlead frame material, thickness and configuration.

While the invention has thus far been described in terms of reducing theincidence of die coat damage due to filler particles, it should also berecognized that the use of the stress relief between the leads and thedie enhances the uniformity of the flow front of encapsulant, andreduces the tendency toward formation of voids by promoting flow of theencapsulant over, under and around the leads and over the die surface.It is believed that improved PRT (Preconditioned Reflow Test, alsotermed a “popcorn” test by virtue of its deleterious effect onsubstandard package integrity) performance, indicative of reduced levelsof moisture in the cured encapsulant, will be realized. However, thishas yet to be empirically demonstrated.

The present invention has been disclosed in terms of certain preferredembodiments as illustrated and described herein. However, those ofordinary skill in the art will recognize and appreciate that it is notso limited, and that many additions, deletions and modifications to, andcombinations of, the disclosed embodiments may be effected withoutdeparting from the scope of the invention as hereinafter claimed. Forexample, the methods used to form a stress relief may include any knownor contemplated method in the art. Multi-layer LOC lead frames such as atwo-frame LOC assembly (see above-referenced U.S. Pat. No. 5,461,255)may be adapted to the present invention. Further, the invention is notlimited to a particular arrangement of leads, or to a particular leadcross-section or configuration.

What is claimed is:
 1. A semiconductor die assembly encapsulated inplastic having filler material therein having a particle sizedistribution and an average particle size diameter within the particlesize distribution during an encapsulation process in a mold, said dieassembly comprising: a semiconductor die having an active surface and aplurality of sides; at least one adhesive segment having an outer edgeand adhering to a portion of said active surface of said semiconductordie; and a lead frame including a plurality of lead members, at leastone lead member of the plurality of lead members having a lead endportion connected to a portion of the lead frame, having a length,having a thickness, and having a free end portion extending over aportion of said active surface of said die, said at least one leadmember including a stress relief portion formed in said at least onelead member of said plurality of lead members, said stress reliefportion extending over a portion of said active surface of said die,extending along a portion of the length of said at least one lead memberat a location between said free end portion and said lead end portionand extending partially through the thickness of said at least one leadmember, said stress relief portion formed in said at least one leadmember extending along the length of the at least one lead member from alocation proximate the outer edge of said at least one adhesive segmentto a location proximate a side of said plurality of sides of saidsemiconductor die, said stress relief portion providing an enlargedspace between a lower surface of said at least one lead member and aportion of the active surface of said semiconductor die, said enlargedspace allowing said plastic having said filler material therein havingsaid particle size distribution and said average particle size diameterwithin the particle size distribution to flow therethrough without saidfiller material therein substantially damaging said portion of saidactive surface of said semiconductor die during said encapsulationprocess of encapsulating said semiconductor device in said plastichaving said filler material therein.
 2. A semiconductor die assemblyencapsulated in plastic having filler material therein having a particlesize distribution and an average particle size diameter within theparticle size distribution during an encapsulation process in a mold,said die assembly comprising: a semiconductor die having an activesurface and a plurality of sides; at least one adhesive segment havingan outer edge and adhesively secured to a portion of said active surfaceof said semiconductor die; and a lead frame including a plurality oflead members, at least one lead member of the plurality of lead membershaving a lead end portion connected to a portion of the lead frame,having a length, having a thickness, and having a free end portionextending over a portion of said active surface of said die, said atleast one lead member of said plurality of lead members having a firstportion of the length thereof adhered to said active surface of saidsemiconductor die and having a second portion of the length thereofextending outwardly over said active surface unadhered thereto, said atleast one member having a stress relief portion formed in said at leastone lead member of said plurality of lead members, said stress reliefportion extending over a portion of said active surface of said die,extending along a portion of the length of said at least one lead memberat a location between said free end portion and said lead end portionand extending partially through the thickness of said at least one leadmember, said stress relief portion formed in said at least one leadmember extending along the length of the at least one lead member from alocation proximate the outer edge of said at least one adhesive segmentto a location proximate a side of said plurality of sides of saidsemiconductor die, said stress relief portion providing an enlargedspace between a lower surface of said at least one lead member and aportion of the active surface of said semiconductor die, said enlargedspace allowing said plastic having said filler material therein havingsaid particle size distribution and said average particle size diameterwithin the particle size distribution to flow therethrough without saidfiller material therein substantially damaging said portion of saidactive surface of said semiconductor die during said encapsulationprocess of encapsulating said semiconductor device in said plastichaving said filler material therein.
 3. The die assembly of claim 2,wherein the first portion of the length of said at least one lead memberis adhered to said die by at least one adhesive segment having an outeredge thereof, the outer edge of the at least one adhesive segment beinglocated substantially parallel a side of the plurality of sides of saidsemiconductor die and being located substantially transverse to thelength of the at least one lead member.
 4. The die assembly of claim 3,wherein said stress relief portion extends along the length of each leadmember of said plurality of lead members from substantially the outeredge of said at least one adhesive segment to a location proximate aside of the plurality of sides of said semiconductor die.
 5. The dieassembly of claim 3, wherein said stress relief portion longitudinallyextends along the length of each lead member of said plurality of leadmembers elements from a position substantially overlaying the outer edgeof the at least one adhesive segment to a location substantially beyonda side of the plurality of sides of said semiconductor die.
 6. The dieassembly of claim 1, wherein said stress relief portion is a recessformed in each lead members of the plurality of lead members.
 7. The dieassembly of claim 6, wherein said recess is a transverse slot positionedon an underside of each lead member of the plurality of lead members. 8.The die assembly of claim 7, wherein said slot forms a thinned portionalong a longitudinal length of each lead member of the plurality of leadmembers.
 9. A semiconductor die assembly encapsulated in plastic havingfiller material therein having a particle size distribution and anaverage particle size diameter within the particle size distributionduring an encapsulation process in a mold, said die assembly comprising:a semiconductor die having an active surface and a plurality of sides;at least one adhesive segment having an outer edge thereof, said atleast one adhesive segment being connected to the active surface of saidsemiconductor die; and a lead frame including a plurality of leadmembers, at least one lead member of said plurality of lead membershaving a lead end portion connected to a portion of the lead frame,having a length, having a thickness, and having a free end portionextending over a portion of said active surface of said semiconductordie, wherein a first portion of the length of said at least one leadmember is adhered to said die by said at least one adhesive segmenthaving an outer edge thereof, the outer edge of the at least oneadhesive segment being located substantially parallel to a side of theplurality of sides of said semiconductor die and being locatedsubstantially transverse to the length of the at least one lead member,said at least one lead member having a stress relief portion formed insaid at least one lead member of said plurality of lead members, saidstress relief portion extending over a portion of said active surface ofsaid die, extending along a portion of the length of said at least onelead member at a location between said free end portion and said leadend portion and extending partially through the thickness of said atleast one lead member wherein said stress relief portion formed in saidat least one lead member extends along the length of the at least onelead member from a location proximate a side of the plurality of sidesof said semiconductor die to a location proximate the outer edge of saidat least one adhesive segment, said stress relief portion providing anenlarged space between a lower surface of said at least one lead memberand a portion of the active surface of said semiconductor die, saidenlarged space allowing said plastic having said filler material thereinhaving said particle size distribution and said average particle sizediameter within the particle size distribution to flow therethroughwithout said filler material therein substantially damaging said portionof said active surface of said semiconductor die during the saidencapsulation process of encapsulating said semiconductor in saidplastic having said filler material therein.
 10. The die assembly ofclaim 9, wherein said die assembly further includes: at least oneadhesive segment disposed between at least a portion of said lead endsand substantially adhering to a portion of said active surface.
 11. Asemiconductor die assembly encapsulated in plastic having fillermaterial therein having a particle size distribution and an averageparticle size diameter within the particle size distribution during anencapsulation process in a mold, said die assembly comprising: asemiconductor die having an active surface and a plurality of sides; atleast one adhesive segment having an outer edge and adhesively securedthereby connected to a portion of said active surface of saidsemiconductor die; and a lead frame including a plurality of leadmembers, at least one lead member of said plurality of lead membershaving a lead end portion connected to a portion of the lead frame,having a length, having a thickness, and having a free end portionextending over a portion of said active surface of said semiconductordie, said at least one lead member of said plurality of lead membershaving a first portion of the length thereof adhered to said activesurface of said semiconductor die and having a second portion of thelength thereof extending outwardly over said active surface unadheredthereto, said at least one lead member having a stress relief portionformed in said at least one lead member of said plurality of leadmembers, said stress relief portion extending over a portion of saidactive surface of said die, extending along a portion of the length ofsaid at least one lead member at a location between said free endportion and said lead end portion and extending partially through thethickness of said at least one lead member wherein said stress reliefportion formed in said at least one lead member extends along the lengthof the at least one lead member from a location proximate a side of theplurality of sides of said semiconductor member to a location proximatethe outer edge of said at least one adhesive segment, said stress reliefportion providing an enlarged space between a lower surface of said atleast one lead member and a portion of the active surface of saidsemiconductor die, said enlarged space allowing said plastic having saidfiller material therein having said particle size distribution and saidaverage particle size diameter within the particle size distribution toflow therethrough without said filler material therein substantiallydamaging said portion of said active surface of said semiconductor dieduring said encapsulation process of encapsulating said semiconductordie in said plastic having said filler material therein.
 12. The dieassembly of claim 11, wherein the first portion of the length of said atleast one lead member is adhered to said die by one adhesive segmenthaving an outer edge thereof, the outer edge of the at least oneadhesive segment being located substantially parallel to a side of theplurality of sides of said semiconductor die and being locatedsubstantially transverse to the length of the at least one lead member.13. The die assembly of claim 12, wherein said stress relief portionextends along the length of each lead member of said plurality of leadmembers from substantially the outer edge of said at least one adhesivesegment to a location proximate a side of the plurality of sides of saidsemiconductor die.
 14. The die assembly of claim 12, wherein said stressrelief portion longitudinally extends along the length of each leadmember of said plurality of lead members elements from a positionsubstantially overlaying the outer edge of the at least one adhesivesegment to a location substantially beyond a side of the plurality ofsides of said semiconductor die.
 15. The die assembly of claim 9,wherein said stress relief portion is a recess formed in each leadmembers of the plurality of lead members.
 16. The die assembly of claim15, wherein said recess is a transverse slot positioned on an undersideof each lead member of the plurality of lead members.
 17. The dieassembly of claim 16, wherein said slot forms a thinned portion along alongitudinal length of each lead member of the plurality of leadmembers.